Many, many people have found the procedure below fixed the problems that 5.0.1 started. MUST follow in order even new phones. Except for the recharge cycle , takes 5 mins or so. Fixes a corrupt calibration file. This is done on your IPhone. . NOT iTunes.
.... you need to do the entire process step by step including "draining the battery completely". Without draining the battery, the battery settings will not be recalibrated and the issue will likely remain. again, ALL the steps and the ORDER are important to get this to work.
1. Reset all settings (settings app-> general-> reset)
2 a. Go through initial setup steps (lang, wifi, siri, enable location, etc) and choose setup as new phone (don't worry your apps, data, contacts, mail will still be there). Do NOT restore from iCloud or iTunes (It can copy back corrupt settings)
2 b. If you do get the complete new setup screen with language setup and setup as new phone or restore from iTune/iCloud backup, be sure to go back to #1 and reset all settings again (it should happen the second time)
3. Turn off system location services timezone and iAd (settings -> location services -> system services)
4. Fully discharge battery (until you get the spinning wheel and it shuts off)
5. Fully recharge battery (overnight if possible)
From
https://discussions.apple.com/thread/3484755?start=705&tstart=0